[IANAFA]
Two methods of valuing options:
1.0 Analyze the cap table and the liquidation preferences for any and all preferred stock.
1.1 Adjust based on liquidity [i.e. few companies are IPO'ing these days], an assessment of the good will of the founders toward employees [i.e. are the founders working to make employees rich], and it discount for the time value of money [i.e. opportunity costs].
1.3 Keep in mind that the valuation from a funding round is based on investors receiving preferred stock, not common stock like employees.
1.4 Understand options are not grants. Be clear on the financial requirements for exercising options both in terms of capital investment and tax liability. Assess these against your current and probable future cash assets.
1.5 Know your tolerance for investment risk. Would you invest your cash savings in the company in an equal amount to whatever cash value you assign to the options. And remember that they are options with a vesting period and only have future value and then only if exercised and sold into a market.
2.0 Use "safe harbor" valuation
2.1 It is worth $0.